The present invention relates to a process for controlling a preset industrial robot. More particularly, the invention relates to a process for measuring motion points in a preset industrial robot and for precisely controlling the movements of the robot in accordance with the measured points.
Processes for controlling industrial robots can be categorized into a preset or preprogramming process and a playback process. In the preset process, an operating program is prepared and stored without moving the robot. The stored program is then read out to cause the robot to effect the desired motions. On the other hand, in the playback process, the robot is actually moved and data describing the motions of the robot is stored. As in the case of the preset process, the stored program is read out to cause the robot to effect the desired motions. The preset process is advantageous in that it is suitable for positioning-type robot motions, and no complicated teaching procedure is necessary, although a programming unit is required. The preset process is commonly used to control assembly robots, for example. In actual applications of the preset process, motion points along a desired path of movement of the robot are indicated on a graphical representation, for example, and an operating program is prepared from the graphical representation.
The preset process, although adequate in many applications, is insufficient, for instance, for controlling the machining of a workpiece which has portions requiring a very high degree of accuracy, portions that cannot be followed on a drawing, or portions which are dimensionally different from the corresponding portions on the drawing. Although the playback process can be used in such instances, it requires a complex teaching procedure.
United Kingdom Patent Application No. 2,027,938 A describes a robot control system including an off-line teach-assist apparatus and an on-line control apparatus. Programs can be prepared in the teach-assist apparatus and then transferred to the control apparatus which utilizes the programs for directly controlling a manipulator arm of the robot. The programs utilized by the control apparatus are in the form of a projected fixed path solution, that is, a predetermined, fixed operating path of the manipulator arm. The stored data further includes projected workpiece positions for use in compensating for movement of the workpiece from a reference position. From the precomputed fixed path solution and the projected workpiece positions, movements of the manipulator arm are controlled so as to provide movements of optimum efficiency. That system does not, however, provide for display of data as it is inputted to the teach-assist apparatus nor for display of stored data. Moreover, that system does not provide any way of rapidly supplying most of the necessary coordinates representing the desired path of movement of the robot using a procedure such as a preset process with only positions in areas requiring a very high degree of accuracy being inputted or corrected by actually moving the robot.